Bob Kaplan, May 30, 1933- November 11, 2021

I just learned from a Reddit post that Robert Lee Kaplan has passed on November 11, 2021. (Tribute archive).
Bob and Ellen Kaplan were for many years a constant weekly presence in the Science center at Harvard, teaching his Math circle (since 1994). My own son has gone for a semester to his math circle and I have sat in to Bob's classes a couple of times. He would often teach just across the elevators in the third or forth floor. It was amazing to see how much young mathematical talent (*) came together there. It was almost intimidating. It had certainly been a bit for my son. Some of the students there came well prepared and were ambitious.

(*) I personally do not believe in mathematical talent. It is preparation, exposure, interest, passion and dedication that matters. CPU, memory etc are essentially the same for all humans.
We also talked a couple of times about math and teaching and what he would do in his math circle classes. Bob and Ellen even had an office in the 4th floor of the math department, very close to my office. When my son participated in the math circle as a student, Bob would cover (for middle school or younger students) the Dehn invariant of polyhedra. An other topic would be complex numbers. We also talked about geometry, especially during the time, when Bob and Ellen were writing their book: Hidden Harmonies: The lives and Times of the Pythagoreans.

Bob was also connected in the department. Until maybe 2014, there has been the tradition that course meetings would take place in the faculty club at Harvard (some course heads would even invite course assistants to come for the lunch meeting). The faculty club was a frequent meeting place for Putnam dinners, for faculty dinners, for staff meetings as well as some conferences or course meetings. This was possible because of a more casual room in the club, where one could get food from a buffet and where one just had to flash a code to have everything payed for. A lot of times, I saw Bob Kaplan there also, meeting with math faculty like Barry Mazur discussion mathematics. The lower part of the faculty club was later dissolved and the club became more exclusive. Thinking of undergraduate students, students, staff and faculty all mingling together in a faculty club is almost unthinkable these days. But it has happened for the majority of time, I have been at Harvard.

Bob and Ellen (and Andy Engelward, who was organizing and teaching that branch of the Math circle for many years) have asked me a couple of times to give guest lectures for the more advanced math circle for older kids at Northeastern university. I have given 8 guest lectures there, from 2003 to 2014 See this page with slides and handouts for each.

Bob fortunately is still present in his book and on youtube talks like this one:
Document history: Feb 17, 2022 posted.